Workflow Evansville

Combined Sewer Overflow

When Evansville’s sewers become too full due to heavy rain or snowmelt, sewer pipes can overflow, and untreated stormwater and wastewater enters the Ohio River and Pigeon Creek. This is called a combined sewer overflow (CSO).

Dangers of CSOs

CSOs contain municipal and industrial wastes, floating debris and disease-causing pathogens, and other contaminants. Eliminating CSOs greatly improves water quality. View real-time status of all CSOs.

What is a CSO?

U.S. EPA’s National CSO Policy

In 1994, the U.S. Environmental Protection Agency (EPA) issued the National CSO Policy, which was incorporated into Section 402(a) of the Clean Water Act. The Clean Water Act, enforced by EPA and Indiana Department of Environmental Management (IDEM), mandates the control of CSOs in Indiana. Approximately 10 cities in Indiana, including Evansville, entered into a consent decree – a binding legal agreement – with the EPA, the U.S. Department of Justice and IDEM to comply with the CSO policy. 

Renew Evansville

Renew Evansville is the Evansville Water and Sewer Utility’s 25-year plan to improve our City’s sewer system, ensure compliance with the Clean Water Act of 1972, and eliminate almost all combined sewer overflows (CSOs). 

Evansville currently captures approximately 35 percent of wet-weather flow and averages 50 overflows each year. Renew Evansville’s projects will help capture 98 percent of that flow and result in no more than four overflows a year.